The present invention relates to a database system which can file image data through a network system and, more particularly, to a database system for storing medical data including image data such as diagnostic images.
In a database system using a network system, a plurality of nodes of a network system are connected to one or a plurality of data output devices, database systems, and terminals. The data output devices output data to be stored, e.g., image data. The output data is filed in the database. The data filed in the database is retrieved by the terminals.
A practical example of a database system using a network system will be described with reference to FIG. 1. This database system handles, e.g., image data.
The network system shown in FIG. 1 is a loop-like link-type network system. Loop-like common data transmission path 400 is provided with a plurality of nodes 401, 402, 403, 404, and 405. Data, i.e., image data is transferred among nodes 401 to 405 via transmission path 400. In image data transfer, image data to be stored, additional data of the image data, and a procedure signal for allowing data exchange are exchanged.
In the network system having the above arrangement, node 401 is connected to image data generator 406 as a data output device and data generated by generator 406 is output onto transmission path 400. The output data is filed by database system 407 connected to node 402. Database system 407 accumulates image data from generator 406 as an image database. The data stored in database system 407 is retrieved by terminal 408 connected to node 403 and is transferred thereto.
Database system 407 has a memory device for storing data, e.g., a rewritable storage (a so-called erasable storage) such as a semiconductor memory device, a magnetic tape device, and a magnetic disk device, or a non-rewritable storage (a so-called non-erasable storage) such as an optical disc device. In a general database system, either a rewritable storage or a non-rewritable storage is used. Particularly in a database system for storing image data, a memory device having a large memory capacity of several GB (gigabytes) is required. Therefore, a database system for storing image data uses a rewritable storage having a high recording density. An optical disc device requires, however, a long access time of 800 msec to access stored image data while a recording density per optical disc is as high as 3.6 GB. Generally, the larger the memory capacity of a memory device, the longer an average access time required for data to be read out from the memory device. As a result, if a memory device has a large memory capacity, a retrieval time required for the memory content is prolonged in proportion to the access time.
Furthermore, when a non-rewritable storage has written data on its recording medium, it cannot write other data on the same location of the recording medium.
Thus, when the image data is edited, the image before editing is left without being erased, and the amount of data to be stored is further increased.
In this manner, in a conventional database system, when a large amount of data, such as image data, is to be handled, since a considerably large amount of data is stored in a memory device, the memory device must have a large memory capacity while the access time is prolonged, degrading processing efficiency.
Particularly when a medical database system is to be constituted, most of the data used for medical diagnosis, examination, or therapy is image data having a high density and covering a broad range of gradation, e.g., a CT (computed tomographic) image and an MR (magnetic resonance) image. Therefore, a memory device must have a still larger memory capacity while the access time is further prolonged, thus degrading the processing efficiency.